Difference from HTTP
HTTPS URLs begin with "https://" and use port 443 by default, whereas HTTP URLs begin with "http://" and use port 80 by default.
HTTP is insecure and is subject to man-in-the-middle and eavesdropping attacks, which can let attackers gain access to website accounts and sensitive information. HTTPS is designed to withstand such attacks and is considered secure against such attacks (with the exception of older deprecated versions of SSL).
HTTPS is typically slower than HTTP. So when large amounts of data are processing over a port, you can see performance differences between these two.

Yes it is. Port 443 is used for all https sites. If you close it you will not be able to browse or otherwise connect to any secure websites or servers. 443 is the standard port that all web browsers use to establish SSL connections. That's where you get the encrypted end-to-end connection from your browser to a site like a bank. Non-encrypted sites use port 80 for regular http traffic.

If you read the link I provided in my initial post and read the quote you know you are wrong!

If you learn TCP/IP you know you are wrong.

A client (web browser) request a port from the "usually" OS own TCP stack, and in old days only ports from 1025 to around 5000 could be used, nowadays it gets port from 49152 to 65535. They are kept untill the connection closes. The client then contacts the server (https server) which obviously needs to be on a specified port on a specified ip-address (in this case 443) for the client to know who to contact. Now they have established a connection and the server sends whatever data the client wants (or doesn't wants). Then it is closed (there are stuff like keep-alive which reuses the same connection, but that is beyond this post)

As the remote server never initiates a connection to the client, the client does not need to keep a port open.

If you however run your own server, or use p2p software, or two-way communicating software (like skype or some kind of messenger) then you need a port open for listening so the remote party are able to initiate the connection.

A client (web browser) request a port from the "usually" OS own TCP stack, and in old days only ports from 1025 to around 5000 could be used, nowadays it gets port from 49152 to 65535. They are kept untill the connection closes. The client then contacts the server (https server) which obviously needs to be on a specified port on a specified ip-address (in this case 443) for the client to know who to contact. Now they have established a connection and the server sends whatever data the client wants (or doesn't wants). Then it is closed (there are stuff like keep-alive which reuses the same connection, but that is beyond this post)

As the remote server never initiates a connection to the client, the client does not need to keep a port open.

If you however run your own server, or use p2p software, or two-way communicating software (like skype or some kind of messenger) then you need a port open for listening so the remote party are able to initiate the connection.

It proves what I am saying, and that you don't know what is asked in the first post. What little snitch is blocking is the outbound connection to the server on port 443 (i.e. the destination port). Not the port on the client side (source port). If you want to close port 443 on the client, https will still work just fine. Shields up is showing the open ports on the client.

Yes it is. Port 443 is used for all https sites. If you close it you will not be able to browse or otherwise connect to any secure websites or servers. 443 is the standard port that all web browsers use to establish SSL connections. That's where you get the encrypted end-to-end connection from your browser to a site like a bank. Non-encrypted sites use port 80 for regular http traffic.

There is some serious misunderstanding going on here.

You will be able to browse https sites, because your browser, inside the firewall, will initiate the conversation.

What ShieldsUp seems to be saying is that it can see port 443 open from OUTSIDE your LAN.

If you're not running a secure-web server or something of the sort on a machine on your LAN, that's odd. Close it, just for your peace of mind. If you find that breaks some application, then you can always open it again.

You will be able to browse https sites, because your browser, inside the firewall, will initiate the conversation.

What ShieldsUp seems to be saying is that it can see port 443 open from OUTSIDE your LAN.

If you're not running a secure-web server or something of the sort on a machine on your LAN, that's odd. Close it, just for your peace of mind. If you find that breaks some application, then you can always open it again.

How do I close it? My computer setting is: DNS is off, NO sharing, firewall is ON